Among the conventionally-known polygonal cross-sectional frames are ones of a hexagonal closed cross-sectional shape which are employed as frames of vehicles. One example of such polygonal closed cross-sectional frames is disclosed in Japanese Patent Application Laid-Open Publication No. H09-309455 (hereinafter referred to as “patent literature 1”), in which beads are formed on side surfaces of the frame so that the frame can effectively absorb a compressive load applied or input to the frame in the axial direction of the frame even where the frame is of a bent shape.
However, although the polygonal closed cross-sectional frame disclosed in patent literature 1 can efficiently absorb a compressive load input axially thereto, it can hardly absorb a load input thereto at an angle or obliquely to the frame axis. Therefore, there has been a demand for a polygonal cross-sectional frame which can efficiently absorb a load input to the frame obliquely to the frame axis.
Also known are rear vehicle body structures in which a depressing bracket (depressing member) is provided over a silencer disposed between left and right rear frames extending toward the rear of a passenger compartment and in which, at the time of a rear collision of the vehicle with an external obstacle or object, the depressing bracket depresses and displaces the silencer to prevent the silencer from undesirably interfering with a fuel tank disposed in front of the silencer, as disclosed in Japanese Patent No. 3920193 (hereinafter referred to as “patent literature 2”).
However, the rear vehicle body structure disclosed in patent literature 2 would require a relatively great dedicated space over the silencer (vehicle-body-mounted component part) for providing the depressing member. Also, the rear vehicle body structure disclosed in patent literature 2 allows the depressing member to depress and displace the silencer by only a small amount.